Spirometry, rapid FEV1 decline, and lung cancer among asbestos exposed heavy smokers

Our plain-English summary of Spirometry, rapid FEV1 decline, and lung cancer among asbestos exposed heavy smokers, by J.W. Chien, D.H. Au, M.J. Barnett, et al (COPD, 2007).

The study

• Authors: J.W. Chien, D.H. Au, M.J. Barnett, G.E. Goodman
• Journal: COPD
• Published: 2007;4(4):339-46
• Type of article: Randomized trial
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We assessed whether spirometric measurements are associated with the development of accelerated FEV(1) decline and lung cancer among active and previous smokers with a wide range of lung function. Bivariate and multivariate analyses that adjusted for age, intervention arm, smoking status at enrollment and smoking history, years exposed to asbestos, and evidence of asbestosis were used to assess whether baseline FEV(1) and FEV(1)/FVC ratio were associated with accelerated FEV(1) decline and incident lung cancer. The 3,041 participants enrolled from 1985 to 1994 were followed through April 30, 2005. Baseline FEV(1)/FVC ratio<0.7 was significantly associated with an increased risk for rapid lung function decline (OR=1.73; 95% CI 1.31-2.28; p<0.001). Baseline FEV(1)/FVC ratio<0.7 was also significantly associated with an increased risk of developing lung cancer, even when baseline FEV(1) was >80%. Lung cancer risk among participants with baseline airflow obstruction and FEV(1)<60% was 4-fold higher than participants without baseline airflow obstruction and FEV(1)>80% (p<0.001), even among former smokers. These data indicate an FEV(1)/FVC<0.7 among smokers is significantly associated with faster airflow loss, and an increased risk for developing lung cancer, even among those individuals with a normal FEV(1).

In plain English

This study followed 3,041 asbestos-exposed male current and former smokers in CARET, a lung cancer prevention trial, from enrollment (1985 to 1994) to April 30, 2005. The authors asked whether baseline breathing-test (spirometry) results were linked to faster lung function loss and lung cancer. At the start, 35% had airflow obstruction (FEV1/FVC below 0.7). In adjusted models, obstruction was associated with rapid decline among current smokers (odds ratio 1.73; 95% CI 1.31 to 2.28). Among former smokers it was not statistically significant (odds ratio 1.16; 95% CI 0.91 to 1.49). There were 206 non-mesothelioma lung cancers, in 12% of men with obstruction versus 4% without; overall, obstruction carried a hazard ratio of 2.23 (95% CI 1.66 to 3.01). Another analysis combined obstruction and FEV1, comparing against men without obstruction whose FEV1 was at least 80% of predicted. Risk was highest with obstruction plus FEV1 below 60% (hazard ratio 3.93; 95% CI 2.51 to 6.15). Obstruction with FEV1 at least 80% also carried higher risk (hazard ratio 2.37; 95% CI 1.35 to 4.16). The authors said the findings need confirming in people not exposed to asbestos.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Cohort analysis of the asbestos-exposed group within CARET, a double-blind, placebo-controlled lung cancer chemoprevention trial, with baseline and yearly spirometry and follow-up for lung cancer
• Who was studied: 3,041 men (100% male) who were current or former smokers with occupational asbestos exposure. They were enrolled in CARET at 5 study centers from 1985 to 1994 and followed through April 30, 2005. For comparison, 116 never smokers were also assessed. Mean age at baseline was 57.3 years, and mean smoking history was 42 pack-years.
• Exposure: Occupational asbestos exposure in a high-risk trade for at least 5 years, beginning at least 10 years before enrollment. Alternatively, participants could qualify with chest X-ray changes consistent with asbestos-related disease plus an occupational history of asbestos exposure. High-risk trades were asbestos worker, boilermaker, plasterboard worker, electrician, plumber/pipe fitter, ship scaler, ship fitter, sheet metal worker, or other. Mean time in high-risk trades was 19 years. Fiber types were not reported. All participants were also exposed to cigarette smoke.
• Main results:
  • At baseline, 1,058 of the 3,041 smokers (35%) had airflow obstruction (FEV1/FVC below 0.70).
  • Participants with airflow obstruction at baseline lost lung function faster. Their FEV1 fell 1.23 percent of predicted per year (SD 3.0), versus 0.76 percent per year (SD 2.3) among those without obstruction, p less than 0.001. In unadjusted comparisons, this was true for both current smokers (p = 0.002) and former smokers (p = 0.01). The trends did not reach statistical significance when adjusted for baseline FEV1.
  • In adjusted models, current smokers with baseline FEV1/FVC below 0.7 had higher odds of rapid FEV1 decline (fastest quartile of the cohort) than current smokers with a ratio of 0.7 or more: OR 1.73 (95% CI 1.31 to 2.28; p less than 0.001). Among former smokers the adjusted estimate was not statistically significant: OR 1.16 (95% CI 0.91 to 1.49, p = 0.24).
  • In unadjusted analysis, years in a high-risk trade did not appear to influence the rate of FEV1 decline. Chest X-rays positive for both parenchymal and pleural changes were associated with rapid FEV1 decline compared with negative X-rays: OR 1.35 (95% CI 1.08 to 1.7).
  • There were 206 cases of non-mesothelioma lung cancer during follow-up.
  • Lung cancer occurred in 125 participants (12%) with airflow obstruction versus 80 (4%) without. In the adjusted Cox model comparing all participants with obstruction against all without, airflow obstruction was associated with a hazard ratio of 2.23 (95% CI 1.66 to 3.01, p less than 0.001).
  • In a separate model, lung cancer risk rose as baseline FEV1 fell, compared with FEV1 of 80% or more of predicted. Hazard ratios were: FEV1 70 to 80%, HR 1.52 (95% CI 1.01 to 2.26); FEV1 60 to 70%, HR 2.19 (95% CI 1.46 to 3.29); FEV1 below 60%, HR 2.94 (95% CI 2.0 to 4.32).
  • With FEV1 and FEV1/FVC in the same model (all participants), the reference group was no obstruction with FEV1 of at least 80% of predicted (37 cases among 1,281, 3%). Participants with obstruction and FEV1 below 60% of predicted had HR 3.93 (95% CI 2.51 to 6.15), with 54 cases among 360 (15%).
  • Participants with obstruction but FEV1 of at least 80% of predicted also had higher lung cancer risk than the same reference group: HR 2.37 (95% CI 1.35 to 4.16, p = 0.003), with 19 cases among 218 (9%). Among former smokers alone, this subgroup's HR was 2.16 (95% CI 0.93 to 5.03, p = 0.07), which did not reach statistical significance.
• The authors' conclusion: The authors concluded that, among smokers, airflow obstruction (FEV1/FVC below 0.7) was associated with faster loss of airflow and with an increased risk of developing lung cancer, even among those with a normal FEV1.
• Limitations the authors state:
  • All participants were exposed to asbestos, which may affect lung function. The authors said the findings need to be validated in a cohort not exposed to asbestos before they are applied to all smokers.
  • The study included only men, so the results may not apply to women.
  • The results are subject to a 'healthy survivor effect': people able and willing to do breathing tests tend to be healthier. The authors believed this would bias results toward finding no association.
  • The analysis did not account for changes in smoking during follow-up.
  • Lung volumes were not measured, so restrictive lung disease could not be confirmed. The authors suspected that restriction might partly reflect asbestos exposure.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Spirometry, FEV1, Lung Cancer, Obstructive Lung Disease.

Related studies

• Estimated intake of vitamin D and its interaction with vitamin A on lung cancer risk among smokers — T.Y. Cheng, G.E. Goodman, et al. (2014)
• CARET, the beta-carotene and retinol efficacy trial to prevent lung cancer in asbestos-exposed workers and in smokers — G.S. Omenn, G. Goodman, et al. (1991)
• Methylation-derived Neutrophil-to-Lymphocyte Ratio and Lung Cancer Risk in Heavy Smokers — L. Grieshober, S. Graw, et al. (2018)
• Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial — G.S. Omenn, G.E. Goodman, et al. (1996)
• The protective effect of beta-carotene and retinol on ventilatory function in an asbestos-exposed cohort — P. Chuwers, S. Barnhart, et al. (1997)
• Recruitment for the beta-carotene and retinol efficacy trial (CARET) to prevent lung cancer in smokers and asbestos-exposed workers — G.S. Omenn, G. Goodman, et al. (1992)

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